Use unitMember/classMember/parameter names instead of offsets in index.

pkg/analyzer/lib/src/summary/idl.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * This file is an "idl" style description of the summary format.  It
  * contains abstract classes which declare the interface for reading data from
  * summaries.  It is parsed and transformed into code that implements the
  * summary format.
  *
@@ skipping 696 matching lines @@
 
   /**
    * Each item of this list corresponds to a unique referenced element.  It is
    * the kind of the synthetic element.
    */
   @Id(5)
   List<IndexSyntheticElementKind> get elementKinds;
 
   /**
    * Each item of this list corresponds to a unique referenced element.  It is
-   * the offset of the element name relative to the beginning of the file.  The
-   * list is sorted in ascending order, so that the client can quickly check
-   * whether an element is referenced in this [PackageIndex].
+   * the identifier of the class member element name, or `null` if the element is
+   * a top-level element.  The list is sorted in ascending order, so that the
+   * client can quickly check whether an element is referenced in this
+   * [PackageIndex].
    */
-  @Id(1)
-  List<int> get elementOffsets;
+  @Id(7)
+  List<int> get elementNameClassMemberIds;
 
   /**
    * Each item of this list corresponds to a unique referenced element.  It is
+   * the identifier of the named parameter name, or `null` if the element is not
+   * a named parameter.  The list is sorted in ascending order, so that the
+   * client can quickly check whether an element is referenced in this
+   * [PackageIndex].
+   */
+  @Id(8)
+  List<int> get elementNameParameterIds;
+
+  /**
+   * Each item of this list corresponds to a unique referenced element.  It is
+   * the identifier of the top-level element name, or `null` if the element is
+   * the unit.  The list is sorted in ascending order, so that the client can
+   * quickly check whether an element is referenced in this [PackageIndex].
+   */
+  @Id(1)
+  List<int> get elementNameUnitMemberIds;
+
+  /**
+   * Each item of this list corresponds to a unique referenced element.  It is
    * the index into [unitLibraryUris] and [unitUnitUris] for the library
    * specific unit where the element is declared.
    */
   @Id(0)
   List<int> get elementUnits;
 
   /**
    * List of unique element strings used in this [PackageIndex].  The list is
    * sorted in ascending order, so that the client can quickly check the
    * presence of a string in this [PackageIndex].
@@ skipping 2029 matching lines @@
    */
   @Id(11)
   int get visibleLength;
 
   /**
    * If a local variable, the beginning of the visible range; zero otherwise.
    */
   @Id(12)
   int get visibleOffset;
 }